air flow

[tonydevon]

Just trying to understand something

Take for example a 28mm dellorto. You can run it open mouthed or fit a pod filter straight to the carb. Simple

What about when you fit an elbow like the breathsweet or the innocenti stock elbow.

Will it be fine so long as the cross section area of the bore is the same or larger than the carb?

In my application i have fitted an innocenti elbow with a ramair filter on the end. The big shock was that at the dyno the jetting wasnt far from stock. No what i expected and the power figure was low.

This got me wondering about restrictions. The exhaust is fine. The stock bike ran a big airbox that wont fit mine.

So even though the bore through the elbow appears to be ok. Could it be restricting the airflow due to the closeness of the bend to the carb?

[fastfrog]

hi tonydevon,
a std innocenti elbow will restrict a lot airflow on a 28 mm carb. to have the best optimized air hose/elbow you need to keep its diameter >2 time your carb diam.... A std elbow looks far from it....

[Agent Buchwald]

Also worth checking is that the standard elbow can collapse slightly at large throttle openings which can restrict it even further.

[warts]

As I'm sure you are aware, removing the air box from most modern bikes can open up a whole mess of worms, and be more than tricky to get back what you loose, let alone see an improvement.
There are rough rules of thumb about what you loose flow wise if you have a corner to negotiate.
For some reason, 50% on a 90degree corner springs to mind, but I can't remember even where to look, let alone anything more precise.
Perhaps a youngster will come along soon. Given time, I'm sure you'll get it right.
Nice build btw.

[tonydevon]

Thanks guys. I have a ram air pod direct on carb now. Its got to go back to dyno anyway so will take all various bits with me and try to see what changes.

[fastfrog]

interesting theory for resonnant air box:

http://www.calsci.com/motorcycleinfo/Airboxes.html